1. Field of the Invention
The present invention generally relates to an air hammer and in particular to a device incorporated in the air hammer for suppressing vibration caused by the operation of the air hammer.
2. The Related Art
Air hammers are widely employed in many fields, such as construction and automobile. Although the air hammer is one of the most commonly used tools in these fields, hazard to an air hammer operator caused by the powerful vibration inherent in the air hammer is the worst drawback for the air hammer. Designers and manufacturers of the air hammer or similar tools have been devoted to the development of vibration reduced or vibration suppressed air tools and such vibration reduced or vibration suppressed air tools are nowadays available in the market.
Examples of the vibration reduced air tools are Taiwan Patent Application Nos. 88219204 and 89204911. The former provides an air chisel comprising a spring based vibration reducing device arranged between an air hammering mechanism and a casing of the air chisel. By means of the resiliency or springing force of the spring based device, the vibration caused by air hammering mechanism is reduced. The later also provides a vibration reducing device comprised of coiled springs arranged on front and rear sides of an air hammering mechanism to suppress the transmission of vibration caused by the air hammering mechanism.
A common drawbacks shared these conventional devices is that the spring is subject to mechanical fatigue after long term and frequent operations. The spring must be replaced once the fatigue occurs. This increases the overall costs of using an air tool. In addition, the springs employed in the vibration reducing devices of the conventional air tools does not ensure a stable behavior in suppressing the transmission of vibration to an operator of the air tools.
Thus, the primary object of the present invention is to provide a vibration suppressing device to be incorporated in an air hammer to overcome the above drawbacks of the conventional air hammering devices.
Another object of the present invention is to provide a vibration suppressing device for air hammer, having a simple structure and thus low costs, to effectively suppress the transmission of vibration caused by an air hammering mechanism of the air hammer.
A further object of the present invention is to provide a vibration suppressing device for air hammer, which has relatively long service life without the need of replacing fatigued parts and which does not adversely affect the output power of the air hammer.
To achieve the above objects, in accordance with the present invention, there is provided an air hammer comprising an air hammering mechanism and a vibration suppressing device to absorb the vibration transmitted from the air hammering mechanism. The vibration suppressing device comprises a cylinder forming a front channel and a rear channel in communication with each other. First and second air passageways are defined in the cylinder and in communication with the front and rear channels respectively. A valve is movably received in the front channel. The valve defines a bore and third air passageways selectively alignable with the first air passageways. A piston is movably received in the rear channel and forms a projection. A jacket surrounds the cylinder to form therebetween an air chamber that communicates the second air passageways. The jacket has a closed end defining a hole into which the projection is selectively received to block the hole. When the air hammering mechanism is driven by compressed air, the compressed air is allowed to simultaneously flow into the valve via the first and third air passageways to move the piston in such a way to have the projection of the piston received into the hole and thus closing the hole for sealing the air chamber. The compressed air is allowed to further flow into the air chamber via the second air passageways. The compressibility of the air inside the sealed air chamber functions to absorb vibration transmitted from the air hammering mechanism.